1. Field of the Invention
The invention relates to an inverter casing.
In the exploitation of energy sources such as PV modules, inverters serve to convert direct current into alternating current. Such an inverter comprises a casing housing electronic power components. These electronic power components comprise, inter alia, components that radiate considerable heat during operation. These components are coils such as chokes in particular.
2. Description of the Prior Art
In this context, a drive unit is known from US 2004/226761 A1, said drive unit comprising a motor, a generator and a gear that are accommodated in a housing, another casing being provided thereon for housing the inverter. The problem of the coils in the inverter radiating heat onto other electric power components of the inverter is not discussed therein.
It is further known that the electronic power components must be protected against environmental impact and in this case more specifically against humidity. Accordingly, casings accommodating such electronic power components have at least the IP65 rating.
On the other hand, it is also known that, through the considerable heat radiation of such coils for example when such type components are mounted in the casing of an inverter, reliability and lifetime of the equipment suffer considerably. A casing accommodating both the electronic power components and in particular coils tries to overcome this problem by separating such coils from printed circuit boards for example through radiation sheets, the function of which consists in preventing as far as possible said coils from directly radiating heat to the printed circuit board. It is thus achieved that the printed circuit board is not subjected directly to the heat radiation, of the coil for example, meaning of a choke for instance. It is however obvious that with such a configuration of an inverter casing the temperature within the casing rises to a constant high value quite shortly after beginning of operation, this being little beneficial to the life time of such an inverter.
In this context, it is known from DE 10 2004 030 457 A1 to accommodate coils outside of the actual casing for the electronic power components. Since the coils need a far lower IP-rating than the typical electronic power components such as printed circuit boards and similar, there is provided to provide the casing part accommodating coils in the form of chokes for example with ventilation slots and at need to also provide for a forced ventilation from the outside through corresponding fans. The advantage of this embodiment is the thermal decoupling of the coils from the other electronic power components in the equipment, so that the temperature inside the casing, meaning in particular in that part of the casing that accommodates the temperature-sensitive electronic power components, can be considerably reduced, this making it possible to considerably increase the lifetime of the equipment and eventually also its reliability.
As already explained above, the electronic power components are to be protected against humidity according to the IP65 rating.
If the chokes for example are accommodated in a special casing part, the connection through the wall to the electronic power components is to be configured so as to meet at least the IP-rating of the casing or casing part accommodating the electronic power components. Another disadvantage is that with this embodiment the coils need to have quite high an IP-rating although they are quite insensitive to humidity. Usually, a separate cover is provided for this casing part accommodating the coils, for the very reason of protecting these coils from UV radiation.
Insofar, it must be noted that, although this construction allows for thermal decoupling between the coils on the one side and the electronic power components on the other side in the casing of an inverter, the expense in terms of construction is still quite high so that an inverter built in this way is expensive.